1. Field of the Invention
This invention relates to, generally, construction materials. More particularly, the invention relates to, structural panels employing lightweight foam filler materials enclosed in a wire matrix to provide, when faced with cementatious coverings, a lightweight, extremely strong building component.
2. Description of the Prior Art
Pre-fabricated structural panels have found increased utilization in the manufacture of certain structures such as houses, factories and other commercial buildings. Such panels are made in a factory to provide lower overall manufacturing costs and allow faster construction than is obtainable with on-site piecemeal construction processes.
The use of lightweight plastic foams such as synthetic resins and expanded plastic foams, such as polyurethane, polystyrene and the like, exhibit a number of properties that are highly desirable as building materials, such as lightweight, low thermal conductivity, impermeability to moisture, and extremely good acoustic and heat insulation. Such materials are already known to be included in structural panels of the type shown in U.S. Pat. No. 4,226,067. In these panels, lightweight expanded polystyrene foam is combined with wire lattices wherein the lattices are machine welded together with a wire mesh to provide an extremely strong, lightweight structural panel. Other examples of prior art structural panels are those found in U.S. Pat. Nos. 3,305,991; 3,555,131; 3,879,908; 4,291,732; 4,297,820; 4,336,676; and 4,340,802.
In these prior art patents, a structural panel and a technique for manufacturing thereof are disclosed in which a 3-dimensional reinforcing framework is first built up and then a lightweight plastic core is formed in situ within the framework, and positioned so that the outer surfaces of the resulting formed-in-place core are, hopefully, located inwardly of the outer boundaries of the 3-dimensional framework.
In U.S. Pat. 4,226,067, by the same inventor, a plurality of elongated foam filler elements are stacked with a flat lattice structure interposed therebetween. The lattice structure contains a sinusoidal strengthening member which is substantially wider than the foam elements. This stacked arrangement is then subject to vertical pressure to cause each of the lattice structures to become imbedded in the contiguous faces of the foam filler members. Thereafter, a wire mesh is welded to the protuding ends of the lattice structures to hold the lattice structures and filler elements in a configuration defining a flat, structural panel.
While this structural panel exhibits physical properties found useful in the construction industry, certain drawbacks exist that render the panels less than satisfactory in many situations. For instance, for welding the wire mesh to the exposed ends of the lattice structures, a space of at least three-fourths of an inch must be maintained between the wire mesh and the surface of the foam to allow the machine welding heads to grasp the intersecting wires to achieve a good weld. Thereafter, a substantial amount of plaster must be used to fill the space between the foam and the exposed ends of the lattice structure. This heavy layer of plaster causes the structure to be heavier than desired.
Further, machines designed to make these foam-filled panels of the prior art require a substantial plurality of welding heads, each fixed at a specific location to make the welds necessary for a full panel. These are situations, for instance when a panel is to be used as a flooring panel, wherein a heavier wire is desired to be made a part of the mesh or wires welded to the exposed ends of the lattice member. In these situations, a heavier wire cannot be utilized with these machines without adjusting the numerous welding heads and their spaced distance from the foam and adjusting the current applied during the welding process. These adjustments slow the manufacturing process and increase panel manufacturing costs. In addition, there are situations where panels are desired to be made with foam elements of 6 inches, 8 inches, 10 inches and 12 inches in size. Under present processes, none of the machinery of the prior art can make these different size panels without extensive re-calibration and resetting of the welding heads, thus slowing the manufacturing process and increasing overall costs.
Still further, in the prior art, if any panel is cut at an angle,the cutaway portion is totally useless for any further structural need. That is, the foam members are interconnected through the welded lattice structures and, thus, are unavailable for piecemeal utilization. The structural panels of the prior art also use solid foam elements that require partial cutting away for introduction of electrical wires and piping into the wall. Finally, it has been determined that the welding of the wire mesh to the exposed ends of the lattice structure causes noticable weakening in the metal wire adjacent the welds thus weakening the overall integrity of the structure. While the manufacturing and assembly costs of the panels remain low, the necessity to cut away part of the foam to allow passage of wires and pipes interior of the wall requires more handwork than normal, thus, increasing these assembly costs.